The overall objective of this proposal is to examine the cell-mediated immunologic (CMI) cross reactions between leukocytes from human breast cnacer TAA and known or putative mammary tumor viruses (MMTV & MPMV) and associated antigens. The intent of this study is the determination of the usefulness of CMI assays for the early diagnosis and monitoring of breast cancer. LBI proposes to examine the CMI responses of breast cancer patients and appropriate control groups in the leukocyte migration inhibition (LMI) assay to MMTV and subviral components.